#pragma once
namespace exercise
{
	template<class T>
	class vector
	{
	public:
		typedef T* iterator;
		typedef const T* const_iterator;

		vector()
			:_start(nullptr)
			,_finish(nullptr)
			,_end_of_storage(nullptr)
		{}

		size_t capacity() const
		{
			return _end_of_storage - _start;
		}

		size_t size() const
		{
			return _finish - _start;
		}

		void reserve(size_t n)
		{
			if (n > capacity())
			{
				size_t sz = size();
				T* tmp = new T[n];
				if (_start)
				{
					for (size_t i = 0; i < sz; i++)
					{
						tmp[i] = _start[i];
					}
					delete[] _start;
				}
				
				_start = tmp;
				_finish = _start + sz;
				_end_of_storage = _start + n;
			}
		}

		void push_back(const T& x)
		{
			if (_finish == _end_of_storage)
			{
				reserve(capacity() == 0:4 : capacity * 2);
			}
			*finish = x;
			++_finish;
		}

		vector(size_t n, const T& value = T())
			:_start(nullptr)
			, _finish(nullptr)
			, _end_of_storage(nullptr)
		{
			reserve(n);
			while (n--)
			{
				push_back(value);
			}
		}

		iterator begin()
		{
			return _start;
		}

		iterator end()
		{
			return _finish;
		}
		
		const_iterator begin() const
		{
			return _start;
		}

		const_iterator end() const
		{
			return _end;
		}

		bool empty()
		{
			return _start == _finish;
		}

		void pop_back(const T& x)
		{
			assert(!empty());
			--_finish;
		}

		T& operator[](size_t pos)
		{
			assert(pos < size());
			return _start[pos];
		}

		const T& operator[](size_t pos) const
		{
			assert(pos < size());
			return _start[pos];
		}

		iterator insert(iterator pos, const T& val)
		{
			assert(pos >= _start && pos <= _finish);
			if (_finish == _end_of_storage)
			{
				size_t len = pos - _start;
				reserve(capacity() == 0 ? 4 : capacity() * 2);
				pos = _start + len;
			}
			iterator end = _finish - 1;
			while (end >= pos)
			{
				*(end + 1) = *end;
				end--;
			}
			*pos = val;
			++_finish;
			return pos;
		}



	private:
		iterator _start;
		iterator _finish;
		iterator _end_of_storage;

	};
}